1. Field of the Invention
The invention relates to a system for changing a program stored in a terminal device, and more particularly to such a system which makes it possible for a terminal device to add programs having necessary functions, remove programs having unnecessary functions, and prevent a third party from illegally downloading a program. The invention further relates to a terminal device used in such a system, and a method of changing a program stored in a terminal device.
2. Description of the Related Art
In connection with the above-mentioned terminal device, Japanese Unexamined Patent Publication No. 7-219780 has suggested a system of downloading a program to a terminal device from a center.
However, the system suggested in the Publication is accompanied with a problem that it is impossible to readily add programs having necessary functions and remove programs having unnecessary function. This is because overall functions of the terminal device are constituted as one program. Hence, the program cannot be partially removed. In addition, since it is impossible to make a vacancy in an area in which a program is stored, additional programs cannot be written into the terminal device.
Furthermore, the above-mentioned system is accompanied with a problem that when a user operates the terminal device for downloading a program thereinto, it would not be possible to prevent a third party from downloading a program to a his/her terminal device.
This is because that the above-mentioned system is not provided with a function of security check.
Japanese Unexamined Patent Publication No. 3-158961 has suggested a system of maintaining a software in processors, comprising first processors each equipped in a shop, and a second processor equipped in a center and connected to the first processors through wide area network (WAN). Each of the first processors includes means for storing data about a software stored therein, and means for transferring a file. The second processor includes means for storing latest data bout a software to be stored in the first processors, means for retaining a load module of the software, means for comparing data about a software transmitted from the first processors to the latest data about the software, and transmitting a load module of the software corresponding to a difference between the compared data, to the first processors, and means for transferring a file. On receipt of the data about a software stored in the first processors, the second processor compares the received data to latest data about a software stored in the first processors, which latest data is stored in the second processor, and transmits a load module corresponding to a difference between the compared data, to thereby automatically update a software stored in the first processors.
Japanese Unexamined Patent Publication No. 9-251714 has suggested a system of controlling a use of a software. In accordance with the system, when an application dealing with a plurality of data is to be used, a software provider may restrict a use of the application, cancel restriction for a use of the application, or set the restriction again in response to a user's request.
Japanese Unexamined Patent Publication No. 5-316206 has suggested a system for executing a program downloaded from an exchanger of a parent station to thereby carry out telephone exchange. The system includes a central processing unit having a read only memory in advance storing a program therein, EEPROM downloading additional and revised programs other than the program stored in the read only memory, from a parent station, and storing the programs, a random access memory copying the programs stored in the read only memory and EEPROM, and a micro-processor executing the programs copied by the random access memory. The system does not download all the programs into a remote control exchanger from an exchanger of the parent station, but downloads only the additional and revised programs into the remote control exchanger.
Japanese Unexamined Patent Publication No. 10-326192 has suggested a system of downloading a software program into a CATV terminal device. The system includes a host device and terminal devices. A software program for operating a terminal device, stored in the host device, is downloaded to the terminal device from the host device to thereby update a software program stored in the terminal device. A software program is stored in each of the terminal devices in a predetermined area in the form of a plurality of program parts, by means of a divider which physically partitions an area of a memory equipped in each of the terminal devices. The software program is stored in the host device in the form of program parts corresponding to the program parts of each of the terminal devices. When the program is to be downloaded, only necessary program parts among the software program stored in each of the terminal devices are updated.
However, the above-mentioned problems remain unsolved even by the systems suggested in the above-mentioned Publications.